Box stay tape



Aug. 10, 1937. F. F. NEWKIRK BOX STAY TAPE Filed June 25, 1936 Vl IFH Patented Aug. 1o, 1937 UNITED STATES PATENT OFFICE BOX STAY TAPE Application June 25, 1936, Serial No. 87,209

1 Claim.

This invention relates to an adhesive tape; more especially to an adhesive tape for use in fabricating cartons, said tape to seal the seam of such cartons and to have sufficient inherent 5 stretchability to be gummed flat to such cartonseams and then to withstand the stresses set up in the tape by the act of opening the, carton, i. e., of altering its shape from its initial fiat form to a rectangular container.

l0 When a carton is formed in collapsed shape ready for the attachment thereto of adhesive tapes to cement together the edges of the carton forming board or the like it is customary to seal said edges together with an adhesive tape which may be of a gummed fabric or a gummed-paper construction.

Gummed paper tapes, especially two-ply paper tapes, have been proved to be of important utility provided they were made of paper reenforced 2O with suitable unspun strands of fibre. Such tapes so reenforced are now widely used in the fabrication of cartons.

However, since a carton is normally fabricated from corrugated paperv or the like, and receives the gummed tape along its proximate edges while the said carton is still in a collapsed state, it is obvious that the thickness of the carton-wall subjects the seam-sealing tape to a severe stressV which is more severe as to the outer face of such tape than to the inner face thereof, when said collapsed carton is "opened out into rectangular form. This results from the circumstance that the radius of curvature of the exposed tape-face exceeds that of the inner face thereof, as will be evidenced by the accompanying drawing.`

It has become important, in the development of the carton-making industry, to provide as the outer ply of a laminated carton-sealing tape (commonly known as a box-stay tape) a paper which is stretchable to an extent adequate to maintain its carton-sealing utility when the carton is opened out. However, the reenforcedpaper tape, as hitherto used, suffers from its insufficient stretchability.

I have discovered that it is possible to form from suitably reenforced paper a satisfactory carton-sealing or box-stay tape if I give to said paper tape a latent streachability as regards its exposed face, and in devising such paper tape I have provided an important advance over existing box-stay tapes of the herein stated construction.

In the preferred embodiment of my invention I form a carton-sealing tape of two plies of kraft paper, said plies confining between them a layer of unspun reenforcing strands as of sisal, said sisal strands being cemented in place by means of a film of asphalt or the like as used to ply together the two plies of paper, and I use as the outermost ply of paper a creped sheet of kraft or 5 the like, the other ply which serves to receive the gum of the gummed-tape product being preferably, but not necessarily, of uncreped structure. Y

From this improved and novel construction it results that a tape so formed may be glued to a l0 collapsed carton, and firmly adhered thereto along the seams of said carton, and said tape'will thereafter remain undisturbed and intact when the collapsed carton is opened up in the above sense. 15

Experience with my invention has proved that a tape so made is component to endure the stresses imposed on it even if the creping of the outer face or ply thereof is done in the usual manner; i. e., with the lines of creping running transversely of the creped-paper sheet; that is, with the larger factor of expansibility of the creped sheet effective, not across the tape, but longitudinally thereof.

By preference I make my tape with an exposed face of paper creped to give to the paper its larger expansibility or stretch across the face of the tape, butcreping so formed as to produce this optimal effect is more costly than the usual transverse creping, and I have found that creped paper as formed with its maximum stretchability in the longitudinal direction possesses suilicient transverse stretch to serve my purpose.

In the accompanying drawing, Fig. 1 shows in cross-section, the construction of my improved tape, and is taken across the lateral dimension of the tape.

Fig. 2 shows my tape positioned upon and across the seam of a wall of a collapsed carton, both shown in cross-sectional elevation.

Fig. 3 shows my tape in position when the carton of Fig. 2 is expanded or opened out, in cross-sectional elevation.

In Fig. 1, a is the ply of stretchable paper, b the intermediate cementitious material having strands of reenforcing fibre deposited in it. These strands if lying in the plane of the drawing are indicated by c, and at c' are shown other strands as cut by the plane of the drawing. "d is another ply of paper, and at e is indicated 50 thereupon a film of adhesive material.

In Fig. 2 the wall of a carton, here formed of corrugated pulp-board construction, is indicated at L f, representing the abutting ends of the wall structure separated by the usual small gap 55 a. LUM m and acres the gap is the tape of Flg. 1, its ts indicated by the reference letters med in Fig. 1.

In Fig. 3 the relation of parts, identically indi- 5 cated, is shown after the carton has been "opened up. Here is ted the distortion of the tape incimt to the shape of the carton wall, and the manner in which the outer ply 'of stretchable paper of the tape has accommodated itself to the changed position by expansion.

Itwlllbeobvhusfrom thisdrawlng theta box-stay tape E subjected. as to itsfouter face, toastressetupwithmits structure by the deformation it when strained around the corner of a carton upon the "opening up" 0f such carton. To an immaterial extent the inner face or ply of the tape is also strained, but normally-made paper is competent to endure this. The outer face however is'strained to a degree suchthatthepaperplieswillseparate.

nom this l of imposed upon the paper plies, (the stress imposed upon the outer ply being excessive) it often results that a two-ply paper tape will ultimately fail.

v That is to say, the excessively stressed outer ply ofpapervwiliyield to the strain and will cleave away from the remaining tape-structure. When this occurs, the tape as a whole is weakened; the imposed by forming the carton into its form will then fall upon the remaining tape and the effectiveness of the tape willbe reduced to a degree such that the carton will no longer be adequately cemented together. If, upm the incidence of a stress too small to muy tm tape as a whole, the outer paper ply thereof breaks away, then the remainingsuishmeofthetamstill cemented to the carton-m11, will expose 'upon its revealed lace aiilmofsnchasasphalt and a layer of 40 reenforcing shands no longer concealed and buried in the tape structure. Thus, while the remainingtapestructuremaystill retain suicient tenacity to seal the carton, its acceptability by thecartmindustryislostbyreason oftheun 4,5 sightly face which it exposes.

A further advantage from my invention results from the better bonding of the creped or otherwise treated surface ply of paper to the sementitious material, as asphalt, used to combine the two paper plies. From the circumstance that creped paper or the like has its surfaces broken 5 up into wrinkles or rugosities, it follows that such paper exposes to the cementitious material an area of contact much greater than the area of a plain paper sheet. When these rugosities are lled with the cementitous material and the tape is subjected to the pressure required to ply it together coherently, the result is a rmer bond between the creped paper ply and the underlying structure of the tape than is possible with plain 15 paper used as the top ply.

Thistirmerbond aidsinresistingthetendency of the plied tape, when under the above described, to undergo separation of its plies, and said tape is thus better enabled to maintain 20 its carton-sealing function without los of its surface ply.

It will be obvious that I may apply to my improved tape, during its fabrication, an adhesive A to serve in cementing it to a carton or the like, 25

or alternatively I may omit to form this adhesive lm and leave to the' carton-maker the operation of applying such film either to the tape or the carton at the time of sealing the seam of said carton. 30

Having thus described my invention, in characteristic terms, and without limitation of my invention to the illltrative citations thereof. above disclosed, A

I claimzv y A tape for the closure of carton seams and corners comprising an outer ply of creped paper,

1 an inner ply of plain paper, and a cementitious binder between said plies. said binder confining within its mass a plurality of reenforcing brous strands, and said tape having upon me exposed face of its plain-paper ply a film of adhesive.

FRANCISF. 

